The human placenta: a novel source of inhibin

Human placental extracts contain inhibin bioactivity and immunoactivity giving dose response curves parallel to a human follicular fluid inhibin standard. Inhibin bioactivity in vitro was neutralised by preincubation of extracts with antisera raised to pure bovine inhibin. Umbilical cord blood from term infants contained immunoactivity. Human placental inhibin differs from human ovarian inhibin in terms of its biological: immunological ratio.